The present disclosure relates to an imaging device, an imaging apparatus, a semiconductor device and a readout method. In particular, the present disclosure relates to an imaging device, an imaging apparatus, a semiconductor device and a readout method which are capable of suppressing a dark current component of a pixel signal.
In the related art, in the imaging device, a charge which is accumulated in a photodiode is read out as a signal level of a pixel signal depending on an accumulation time, and the signal level of the pixel signal is subjected to analogue-digital conversion. Various methods have been proposed in the related art for reading out the pixel signal (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-033452).
For example, in the method taught in Japanese Unexamined Patent Application Publication No. 2006-033452, a pixel signal of the readout period of an n-th row and a reference signal to digitize the pixel signal are compared, a count process is performed in either a down mode or an up mode concurrently with the comparison process, and the count value of the point in time at which the comparison process completes is maintained. Next, using the result of the count process of the n-th row as the initial value, a pixel signal of the readout period of an n+1-th row and a reference signal to digitize the pixel signal are compared, a count process is performed in either a down mode or an up mode concurrently with the comparison process, and the count value of the point in time at which the comparison process completes is maintained. The count value after the count process of the n+1-th row is a subtraction result when the mode of the count process of the n+1-th row is opposite to the count mode of the n-th row, and is an addition result when the count modes are the same.
By adopting such a method of reading out a pixel signal, it is possible to maintain a compact circuit scale of the analogue-digital converter and a low number of transmission signal lines and also to efficiently perform a product-sum operation.